1. Field of the Invention
The present invention relates to a piezoelectric member, a piezoelectric member element, an actuator in use thereof, and a liquid discharge head (an ink jet head) as well as a method of manufacturing the piezoelectric member.
2. Description of the Related Art
Metal oxide ceramics consisting of PZT(Pb(Zr,Ti)O3) system are generally known as a piezoelectric member. These PZT system ceramics have excellent piezoelectric characteristics and are widely used for a piezoelectric actuator, a piezoelectric ignition element, a piezoelectric buzzer, a piezoelectric transformer, and the like. However, a strain amount thereof is around 0.1 to 0.15% even at a maximum and may not be sufficient in the case of being used as a piezoelectric actuator and the like. In recent years, for a purpose of obtaining further piezoelectric characteristics or a large amount of strain, relaxor material is being considered and, for example, Japanese Patent No. 3397538 shows a method of synthesizing PZN-PT and PMN-PT with flux fusion. Such a synthesizing method is reported to derive a bulk type single crystal and give rise to material with a large strain amount in excess of 1%. In addition, forming film directly on a substrate with a film forming method such as a sol-gel method, a hydrothermal synthesis method, a sputtering method, a MBE method, a PLD method, a CVD method, and a MO-CVD method in use of relaxor material is being considered. For example, PMN-PT film is reported to have been formed with a PLD method in Applications of Ferroelectrics, 2002. ISAF 2002. Proceeding of the 13th IEEE International Symposium P133-136.
However, for example, a MEMS piezoelectric actuator, development of which is being proceeded enthusiastically in recent years, is finely structured and therefore, production thereof is very difficult since single crystal is required to be made into thin pieces for junction in the case of using single crystal material which has been caused to grow in a bulk state as described in Japanese Patent No. 3397538.
In addition, the relaxor material has a large relative dielectric constant and can be made into thinner film so that the capacitance of a piezoelectric element gets larger. Accordingly, supply of electric power to drive it gives rise to phase delay of supply power due to a relationship with wire resistance, an issue of delay in drive response to a high frequency drive accompanied thereby, an issue such as a tendency to provide larger driving power supply capacity, and the like.
In particular, for an ink jet head of an ink jet printer where a piezoelectric member element is being utilized as an actuator, a discharge ink droplet is attempted to be made minute in recent years so that a formed image thereof derives a more sophisticated image quality. In addition, a the number of discharge ink droplets required for image forming accompanied thereby tends to increase. In addition, in order to attain high speed, high frequency of supply driving power, intensified density, and extension of ink jet head nozzle is being developed. That is, the ink jet head is required to discharge minute ink droplets stably from a number of ink jet head nozzles at a high driving frequency. Therefore, the issue of delay in drive response to a high frequency drive and the issue of requiring a larger driving power supply capacity are significant problems.
Moreover, in general the relaxor material is accompanied by a relief phenomenon in the dielectric constant due to temperature change and the variation in the dielectric constant due to temperature change will get larger within a temperature range in the actual use range of the piezoelectric member element since a Curie temperature Tc thereof is low when compared with a piezoelectric material such as PZT. Accordingly, the case of application into the ink jet head gives rise to an issue that stable discharge performance cannot be maintained under various use environments and such environments that will increase temperature of a piezoelectric member element due to continued use.